1. Your ROM isn't patched unless the game already has LEDs and the previous owner did it.
2. Buy sample bulbs and compare yourself. I always color match.
3. Buying a pack of the cheapest LEDs and hoping to do your whole game in crappy $0.35 white bulbs is going to look awful. LEDing a game is not a $25 job. I use bulbs of various styles, colors, brightness, and price when doing a game. The whole point is to make your game look better. Make sure you're not paying for a downgrade.